Milliampere meter How much do they cost?

dear friends , I need to measure/confirm current output from a small circuit which maybe upto 4 milliampere, What is the cheapest option avaliable for this and how much it will cost?

Many Thanks for your help in advance

If you want to just check the circuit, use a DMM. Every digital multimeter has a mA scale and they usually cost about Rs.1000/- to Rs.3500/- for average accuracy meters. There are other best quality/accuracy meters but those will cost a lot.

Another possible way is to insert a low value series resistor in the current path, measure the voltage across the resistor and do some maths (I=V/R)

[quote=", post:2, topic:21674"]

If you want to just check the circuit, use a DMM. Every digital multimeter has a mA scale and they usually cost about Rs.1000/- to Rs.3500/- for average accuracy meters. There are other best quality/accuracy meters but those will cost a lot.

Another possible way is to insert a low value series resistor in the current path, measure the voltage across the resistor and do some maths (I=V/R)

[/quote]

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Volt_0-30V.jpg

Many Thanks your for answer .............

What about these pannel meters ? How much do they cost? Does these meters puts any load on circuit?

Actually I need to constantly monitor Milliampere and voltage from a circiuit running on two 9v batteries for 30 minutes and if voltage drops or milliamps increase for any reason I need to turn it off ............... For 30 minutes voltage must be 9v and milliamps must not exceed 4amp ..............

These are low cost meter, ranging from Rs.150 to Rs.300 (just a guess). Ideally an ampere meter should have zero resistance so that it does not affect the load current and a voltmeter should have infinite resistance so that it does not load the circuit.

But things are different in reality so this type of voltmeter will definitely load your circuit (may be 1-2 mA to several mA) and ampere meter will also add it's internal resistance to the circuit.

If you really need to use this type, you will need to find a high sensitivity voltmeter. Remember, it takes current to deflect the needle. A 0-30mA Full scale meter will need 30mA if needle has to move the full scale position. The problem is that you don't find any data with locally available parts. You will be lucky if you can find a sensitive voltmeter like 0-3mA full scale.

[quote=", post:4, topic:21674"]

These are low cost meter, ranging from Rs.150 to Rs.300 (just a guess). Ideally an ampere meter should have zero resistance so that it does not affect the load current and a voltmeter should have infinite resistance so that it does not load the circuit.

But things are different in reality so this type of voltmeter will definitely load your circuit (may be 1-2 mA to several mA) and ampere meter will also add it's internal resistance to the circuit.

If you really need to use this type, you will need to find a high sensitivity voltmeter. Remember, it takes current to deflect the needle. A 0-30mA Full scale meter will need 30mA if needle has to move the full scale position. The problem is that you don't find any data with locally available parts. You will be lucky if you can find a sensitive voltmeter like 0-3mA full scale.

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Just one more question

Since you mentioned these analog meters draw current This is not what I want or afford

Then what about digital pannel meters ? are these avaliable in Pakistan and are these cheap ? I do understand these digital meters will require its own powersource but would these panel meters draw current from circuit ?

$%28KGrHqZ,!qgFHJYIhmz!BR1NzuMWE!~~60_1.

Volt_Ampere_Meter_PIC16F876.jpg

They are available, they are cheap. they may be accurate but they will draw power from circuit.. which will ruin your calculation

as ijaz has explained in detail already, self powered circuit is what you need with no resistance issues.. uni-T meters are highly accurate, self powered and capable of high sensitivity.. digital and multifunctional. around 2800-13000 range, the one costing 3500+/- is ideal for almost every need. AC and DC.

analogue Panel meters are not acurate, fluctuate and you canot hold its reading

Can you share the circuit for me to present a solution.

Are you putting in a panel meter just to test the circuit and it will be mostly redundant afterwards? The drop/change maybe so miniscule that it may not even register on a low cost panel meter.

Aurangzeb

[quote=“aurangzebhaque, post:7, topic:21674”]

Can you share the circuit for me to present a solution.

Are you putting in a panel meter just to test the circuit and it will be mostly redundant afterwards? The drop/change maybe so miniscule that it may not even register on a low cost panel meter.

Aurangzeb

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Below is my simple circuit I need to check current & voltage as long as the circuit is on.........

2zedk5v.jpg

Jamal,

I am afraid that this circuit will need revision.

Can you please indicate the points between which you want to measure the voltage. Also please indicate which current needs to be measured.

Aurangzeb

[quote=“aurangzebhaque, post:9, topic:21674”]

Jamal,

I am afraid that this circuit will need revision.

Can you please indicate the points between which you want to measure the voltage. Also please indicate which current needs to be measured.

Aurangzeb

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Since the regulator's job is to regulat current therefore I want to see a constant supply of 2ma to 4ma at points A and B no matter what change in resistance occur in variable resitance

I donot know where exactly I should connect the meter to measure current

there is another design I found at internet but Its out put is too much

70cr5e.jpg

Use the circuit in the link below

http://circuit-diagram.hqew.net/Adjustable-Constant-Current-Regulator_4681.html

Use a 12 volt battery, with the + terminal connected to the IN terminal of the LM317 in the circuit diagram. The - terminal of the battery will connect to the lower line, on the supply side.

The milliammeter + terminal will connect to the line going to the emitter of BC337. The - terminal of the milliammeter will be + side of the load while - side of the load will go to the bottom line.

Aurangzeb

[quote=“jamalkhan, post:10, topic:21674”]

Since the regulator's job is to regulat current therefore I want to see a constant supply of 2ma to 4ma at points A and B no matter what change in resistance occur in variable resitance

I donot know where exactly I should connect the meter to measure current

[/quote]

do this for measuring current:

2laub7a.jpg

Also, some guy telling you DMMs cost 1000+, I bought a cheap china one (pretty good though) for rs. 250. So there's cheaper ones out there too...

cheap is not equal to quality and accuracy.

[quote=“zedeneye1, post:12, topic:21674”]

do this for measuring current:

2laub7a.jpg

Also, some guy telling you DMMs cost 1000+, I bought a cheap china one (pretty good though) for rs. 250. So there's cheaper ones out there too...

[/quote]

Rs.250 ? where did you get that? is it digital?

Ok GUys anyone who is interested I puchased this multimeter from Hallroad Lahore for just Rs.230

[quote=“jamalkhan, post:15, topic:21674”]

Ok GUys anyone who is interested I puchased this multimeter from Hallroad Lahore for just Rs.230

[/quote]

This is the one I was talking about....It's a cheap chinese one....but it's reasonably okay. Not okay for professional work, but fine for hobbyists doing very basic stuff.